A construction machine such as a hydraulic excavator, a hydraulic crane and the like is generally configured by an automotive lower traveling structure, an upper revolving structure revolvably mounted on the lower traveling structure, and a working mechanism tiltably mounted on a front side of the upper revolving structure. The upper revolving structure mounts an engine on a rear part in a revolving frame for driving a hydraulic pump, and mounts a cab, a fuel tank, an operating oil tank and the like on a front side in the revolving frame.
Here, a diesel engine is generally used as an engine that operates as a prime mover of the construction machine. There are some cases where harmful substances such as particulate matter (PM) and nitrogen oxides (NOx) are contained in an exhaust gas emitted from such a diesel engine. Therefore, the construction machine is provided with an exhaust gas purifying device in an exhaust pipe forming an exhaust gas passage of the engine for purifying an exhaust gas therein.
The exhaust gas purifying device is configured by including an oxidation catalyst (for example, diesel oxidation catalyst, referred to as “DOC” for short) for oxidizing and removing nitrogen monoxides (NO), carbon monoxides (CO), hydrocarbon (HC) that are contained in an exhaust gas, and a particulate matter removing filter (for example, diesel particulate filter, referred to as “DPF” for short) that is arranged downstream of the oxidation catalyst for trapping and removing particulate matter in the exhaust gas (Patent Document 1).
Incidentally, in the particulate matter removing filter, the particulate matter deposits therein following the trapping of the particulate matter, which might cause the filter to be clogged. Therefore, it is necessary to remove the particulate matter from the filter in the point in time where a predetermined quantity of the particulate matter is trapped for regenerating the filter. This regeneration treatment of the filter can be executed in such a manner that fuel injection for regeneration treatment called, for example, “post injection” is performed to increase a temperature of an exhaust gas for burning the particulate matter that has deposited in the filter.
On the other hand, when the regeneration treatment of the filter is executed in a state where the particulate matter is excessively deposited in the filter (excessive deposit), the temperature of the exhaust gas rises to be excessively high (a combustion temperature of the particulate matter is excessively high), which might possibly cause the filter to be melted and damaged. Therefore, the conventional art is configured such that a trapping quantity of the particulate matter trapped in the filter is estimated, and based thereon the regeneration treatment is executed before the estimated trapping quantity becomes excessively large.
More specifically, an emission quantity (generating quantity) of particulate matter that is emitted from the engine is estimated based upon a rotational speed of an engine and a fuel injection quantity, and the regeneration treatment is executed at the time the estimated quantity reaches a preset threshold value (Patent Document 2).
On the other hand, according to the other conventional art, a trapping quantity of the particulate matter trapped in the filter is estimated from a difference (differential pressure) between pressure in an inlet side and pressure in an outlet side of the filter, and the determination on whether or not the regeneration treatment is executed is made based upon the estimated trapping quantity (Patent Document 3).